<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>DownloadTest</title>
</head>
<body>
    
    <a href="javascript:;">求你点一下</a>
    <img src="" alt="abc" style = "display: none">
</body>
<script>
    let img =  document.querySelector("img");
    let a = document.querySelector("a");
    a.onclick = () => {
        
        img.src = 'http://47.96.253.99/SZ_war/downloadFile';
        img.style.display = 'block';
        a.innerHTML = '咳 咳';
        alert("咳！咳");
    }
    
    // let xhr = new XMLHttpRequest();
    
</script>
</html>